As one of conventional power-factor correction methods for a switching power supply device that includes a converter circuit, a chopper circuit, an inverter circuit, and the like, there is a high power-factor converter method in which a smoothing capacitor is mounted on the output side of a boost chopper circuit.
In a switching power supply device using this method, on the output side of a boost chopper circuit, a surge absorbing capacitor intended for surge absorption in a switching element is often connected in parallel to a smoothing capacitor that smoothes a voltage. For example, in Patent Literature 1 mentioned below, a surge absorbing capacitor (a first capacitor) that prevents a phenomenon of output voltage ripples caused by resonant oscillations at the time of starting an operation is provided and connected in parallel to two smoothing capacitors (second and third capacitors) that constitute a π-type smoothing circuit through an inductance, and further a damping resistor is connected in series to the third capacitor.